Current types of high intensity lamps must be powered by a AC power source. New types operable by DC power source have been developed. The power supplies and ballasts of the prior art are each specifically designed to energize and control a single type of high intensity lighting element, and offers little or no control of the light intensity of the lamp. This is due to the fact that those devices employ ferro-resonant transformers which are designed to operate at a single frequency and can only deliver the specific voltage and current required by a particular lamp model. Since the light intensity of the lamp depends upon the lamp voltage rating and the current running through it, the power source of the prior art can not provide a convenient brightness control.
The state of the art is best illustrated in the disclosure of U.S. Pat. No. 4,751,398 Ertz, III which uses an output transformer operating at a high frequency.